Question

Which of the following molecules may have hydrogen bonds between other molecules of the same kind?
Option:
1.$C{H_3}F$
2.$C{H_3}N{H_2}$
3.$C{H_3}OH$
4.$C{H_3}Br$

Answer 1

Hydrogen bond is defined as the attractive interaction between hydrogen atom of a molecule and highly electronegative atom (like nitrogen, oxygen and fluorine) of other molecules. Such interaction is found mainly when the molecule contains nitrogen, oxygen or fluorine atoms bonded with hydrogen.

Complete answer:
To have hydrogen bonding in between molecules, a nitrogen, oxygen or fluorine atom in one molecule and an hydrogen atom bonded to a nitrogen, oxygen or fluorine atom in another molecule is required. So let us take all the options one by one.
$C{H_3}F$ contains a fluorine atom, but does not contain the $H - F$ bond, as all the hydrogen atoms and fluorine atoms are attached to the central carbon atom directly. Thus, it cannot form hydrogen bonds.
$C{H_3}N{H_2}$ contains nitrogen atoms and also contains $N - H$ bond, so hydrogen bonding will be present between two molecules of $C{H_3}N{H_2}$ .
$C{H_3}OH$ contains oxygen atoms and also contains $O - H$ bond, so hydrogen bonding will be present between two molecules of $C{H_3}OH$ .
$C{H_3}Br$ contains bromine which is more electronegative than hydrogen but it does not contain any hydrogen atom attached to oxygen, nitrogen or fluorine. Thus, it cannot form hydrogen bonds.

Hence, the correct options are $C{H_3}N{H_2}$ and $C{H_3}OH$ .

Note:
Hydrogen bonding is a different kind of dipole-dipole interaction, it is not covalent to hydrogen atoms. Hydrogen bonding is of two types, intermolecular hydrogen bonding (between two or more different molecules) or intramolecular hydrogen bonding (within the same molecule).